Just a quick note today: i found the hard way that bgp exist-maps will only work if the prefix is in the bgp table, not in the routing table (e.g. as a connected interface). So if we have a link 13.13.13.0/24 between routers 1 and 3, a network statement must be added under the router bgp <as> section if we want to include this prefix under:
neighbor 1.1.1.1 advertise-map map1 non-exist-map map2
network 13.13.13.0 mask 255.255.255.0
route-map mymap1 permit 10
match ip as-path 1
route-map mymap2 permit 10
match ip address prefix myprefix
